Authors: Julián Naranjo-Vesga (presenter), Darwin Mateus-Tarazona, Instituto Colombiano del Petróleo, Ecopetrol S.A.; Andrea Ortiz-Karpf, Pedro Galindo, Ecopetrol S.A.; Lesli Wood, Zane Jobe, Lauren Shumaker, Colorado School of Mines; Juan Felipe Paniagua-Arroyave, Universidad EAFIT
The distribution of deep-water gravity deposits in the Sinú Fold Belt, offshore Colombia, is the result of the interaction between tectonic deformation and sediment supply. In tectonically deformed areas, anticlinal structures form barriers for sediment transport from the continental shelf to the basin floor, and piggy-back sub-basins act as sediment traps. Three main river systems feed the Sinú offshore basin: The Magdalena, Atrato, and Sinú rivers. The interplay between sediment supply and along-strike variations in structural deformation, results in complicated sediment-flow pathways, determines the geometry of the continental shelf and slope, and controls the distribution and morphometry of deep-water deposits.
This study used approximately 7,736 km2 of 3D seismic and 42,500 km2 of high-resolution multibeam bathymetric data, in order to characterize Pliocene-Recent deep-water gravity-driven deposits along the Sinú offshore basin, analyzing spatial variability and its relationship with shelf and slope morphology and sediment input. The study area was divided in three geomorphological zones: 1) The Northern Zone is characterized by a relatively undeformed slope and high sediment supply from the Magdalena River. In this sector large channel-levee systems that stack vertically for more than 350 m prevail. Most channels start as gullies at the transition between the continental shelf and the slope. In this zone, mass-transport complexes (MTCs) also occur; the larger ones are commonly associated with failures at the shelf edge. MTCs fill bathymetric lows and erode bathymetric highs smoothing the seafloor topography and modifying sediment pathways. 2) The Central Zone highly structurally deformed by NE-SW trending anticlines with steep flanks, separated by piggy-back sub-basins that form a rugose slope profile and act as barriers for sediment transport. This zone is mainly associated with low sediment supply from Sinú River. Submarine canyons are the main conduits for basin-ward sediment transport. They start as gullies on the upper slope and merge downslope to form canyons. Erosion along canyons can breach the anticlines, resulting in the interconnection of piggyback sub-basins and enabling sediments to reach the basin floor. Mass-failures from the steep flanks of structures generate block falls and detached MTCs which commonly run out less than 15 km. 3) The Southern Zone has a moderate sediment supply fed by the Atrato River. Mass wasting has modified sea-floor topography; anticline crests have been eroded and piggyback sub-basins filled, burying the thrust belt and smoothing sea-floor topography. Erosional scours carved by mass failures merge basinward to become submarine canyons on the slope and connecting the slope with the distal basin, where up to 80 km long, MTCs accumulate.
This study documents and analyses the impact of sediment supply, structural deformation and shelf width, on the sedimentary processes and depositional architecture of deep-water deposits along the Sinú offshore basin.
Julián Naranjo-Vesga, Instituto Colombiano del Petróleo (ICP) – Ecopetrol S.A
Julian earned a BSc in Geology from the Universidad Industrial de Santander, Colombia.
With 14 years of experience in the industry, he currently works as a Geologist in the Instituto Colombiano del Petróleo (ICP) – Ecopetrol, S.A. at Piedecuesta, Colombia, bringing support to sedimentology and stratigraphy projects.